Author Topic: head and springs  (Read 439 times)

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Offline tck

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head and springs
« on: 31 May 2020 at 15:39 »
I am not sure about the heads on this engine, not only did it have a 90+ timing cover but I think the head fins are larger than those of my last T35 which I no longer have to compare. the engine number indicates it was originally a MK4 but it was in race trim and my general ignorance of detail Douglas parts has me guessing
Whatever it is what should the valve spring lengths be? were the 90+ springs different.? once I ascertain the heads I can hopefully when spares come back get some correct new ones if not and I have to use these so I would like to know the appropriate lengths to see if these will be within tolerance.


Offline phil1

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Re: head and springs
« Reply #1 on: 01 Jun 2020 at 07:17 »
Hi
       Tim that head looks a bit special with it's carb flange and exhaust stub, the mks just push in, apart from that rockers look the same, have some spare stuff here if you need to look.  Phil 1.

Offline eddie

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Re: head and springs
« Reply #2 on: 01 Jun 2020 at 09:30 »
That is an iron head for a 'Plus' machine. They were fitted with triple valve springs and I have just measured a brand new set of springs - the sizes being:-

   Outer spring -      1.750" long x 1.460" dia x .142" dia wire.  (Wound right handed)
   Middle Spring -     1.750" long x 1.125" dia x .114" dia wire.  (Wound left handed)
   Inner Spring -      1.750" long x   .885" dia x .085" dia wire.  (Wound right handed)

   Regards,
                 Eddie.

Offline tck

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Re: head and springs
« Reply #3 on: 01 Jun 2020 at 09:42 »
Thanks Eddie for helping me round this strangely modified engine

Offline douglas1947

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Re: head and springs
« Reply #4 on: 01 Jun 2020 at 11:38 »
The castle nuts on the rockers (for regulatle the valve clearence) are not original.
There should be used 2 nuts of 1/4" BSF on each thread.

Michael

Offline tck

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Re: head and springs
« Reply #5 on: 01 Jun 2020 at 15:38 »
Yes I thought they were wrong, I did have a close look in case some clever clogs had secured it with a hole and  split pin but no, Not a problem I have plenty of BSF hardware being a Vincent owner.
I couple of fins have bit missing I was going to get them laser welded but the quote was £200! I have made some replacements in cast iron but welding them up seems tricky there are some reports that  a dab dab spot approach with Tig is the way to go?

Offline Vitesse

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Re: head and springs
« Reply #6 on: 01 Jun 2020 at 22:09 »
I couple of fins have bit missing I was going to get them laser welded but the quote was £200! I have made some replacements in cast iron but welding them up seems tricky there are some reports that  a dab dab spot approach with Tig is the way to go?
Where are you? I had asome cast iron welded up locally to me (wife's favourite cast iron pan!) near Coventry Uk.

Offline tck

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Re: head and springs
« Reply #7 on: 02 Jun 2020 at 07:21 »
I am in easy reach of Coventry I understood that conventional welding required pre and post heating to avoid cracks does this company do engine repairs?

Offline douglas1947

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Re: head and springs
« Reply #8 on: 02 Jun 2020 at 16:09 »
I have done several welding repairs on cast iron barrels / heads with CO² welding by my own. But use mild steel for the replacement fins instead of cast iron!

Do you have the original barrels to the heads?
There is a difference to the studs between 90+ and standard barrels.

Michael

Offline tck

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Re: head and springs
« Reply #9 on: 02 Jun 2020 at 16:47 »
Yes I have the correct barrels by co2 welding do you mean tig or mig?

Offline douglas1947

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Re: head and springs
« Reply #10 on: 04 Jun 2020 at 15:58 »
I think it is mig welding.

Michael

 

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